Another panelist at the Monday session said four. A third said six. Only Steve Streit, CEO of prepaid card Green Dot whose company also runs GoBank, said his answer was two and one-half, meaning that Streit sees at least some life for traditional branches.

Chokshi meantime chafed at another question, what’s the ROI of mobile banking? He said, “What’s the ROI of air or water? You need the mobile channel, in the way you need air and water.”

As for why American Express launched Bluebird – essentially a prepaid card with check-writing options – Chokshi said, “There is nothing in our brand values that says we are only for the affluent. The prepaid model lets us serve customers we couldn’t serve before. “

He added that, in his estimate, “a traditional bank has a cost structure two and one-half times higher than ours as a mobile product. The inefficiencies in the current banking model are enormous.”

Streit, too, sang the praises of mobile, pointing to research that suggests a typical person touches his or her cellphone 200 times daily. “Mobile is different from online banking,” he added. “With mobile you always have your bank with you.”

Chokshi added, “Two and one-half billion people do not have bank accounts. But they do have mobile phones. Digital accounts are safe and secure compared to cash. We are looking to expand Bluebird into perhaps South Africa and Mexico – you will see us enter international markets next year.”

Streit added that although he thinks “branches will around a long time,” his goal with GoBank – which has one branch in Provo, Utah - “is to make it into all the bank a customer needs.”